In the "before" part of the figure below, car A (mass 1000 kg) is stopped at a traffic light when it is rear-ended by car B (mass 1600 kg). Both cars then slide with locked wheels until the frictional force from the slick road (with a low µk of 0.14) stops them, at distances dA = 8.2 m and dB = 6.1 m.
(a) What is the speed of car A at the start of the sliding?
(b) What is the speed of car B at the start of the sliding?
(c) Assuming that linear momentum is conserved during the collision, find the speed of car B just before the collision.
(d) Explain why this assumption may be invalid.